1. Field of the Invention
The present invention relates to an electronic musical apparatus that is accessible to plural types of recording medias and can read music content, that is encrypted to be recorded, from one optional recording media among the plural types of recording medias and can encrypt the music content to be recorded to one optional recording media, and to a computer-readable program applied to this apparatus.
2. Description of the Prior Arts
Conventionally, there has widely been known an electronic musical apparatus such as an electronic musical instrument or the like that can make an automatic performance based upon music piece data (performance data) composed of MIDI data. Further, there has been proposed an electronic musical instrument that adopts a memory card such as a smart media (registered trademark) as an external memory media, wherein the prestored MIDI music piece data is read from this memory card for an automatic performance or the MIDI music piece data edited or composed by a user is written in the memory card for storage. Moreover, in case where MIDI music piece data or the like (hereinafter suitably referred to as “music content”) that needs a copyright protection is read from the external recording media or the like, some electronic musical instruments give management information including a copyright flag to the music content for attempting a copyright protection to protect illegal copy.
A CPU adopted in an electronic musical instrument has increased speed year by year. Further, the electronic musical instrument has incorporated therein a recording media such as a flash memory ROM, CD-ROM/R/RW drive or the like or it can be connected to these recording medias via an interface such as a USB or the like. Therefore, various recording medias are being able to be utilized for electronic musical instruments. Using plural types of recording medias described above leads to the use of various software or various contents, thus enhancing a function of the electronic musical instrument. Moreover, the music content can also be recorded in the various recording medias according to the taste of a user. In this case, it becomes necessary to consider the copyright protection of the music content.
From the viewpoint of the copyright protection, a technique for encrypting music piece data is disclosed in Japanese Unexamined Patent Application No. 2003-208163. This conventional technique discloses that music piece data is transmitted via a network and this music piece data is taken in an electronic musical instrument to execute an automatic performance. Further, in this conventional technique, music piece data is encrypted by using a key (secret key) so as not to allow the illegal use of the auditioning music piece data.
When a secret key is used for an encryption as described above, the secret key is needed for its decode. Therefore, it is necessary to store the secret key in, for example, an electronic musical instrument that is also used as a stand-alone device. Moreover, in case where the music contents respectively stored in the plural types of recording medias are encrypted, the use of common secret key simplifies a processing program, but once the secret key is found, the music contents in all the recording medias are easily decoded, thereby entailing a problem that a level of protection is weak, such as allowing an illegal copy.